The present invention relates to fluid driven reciprocating pumps. The invention is particularly applicable to the type of reciprocating pump illustrated in our prior U.S. Pat. Nos. 4,021,149 and 4,548,551, and is therefore described below with respect to this application.
The above two patents describe a reciprocating pump including a pair of heads controlled by a main distribution valve, which latter valve is in turn controlled by a pilot valve. An object of the present invention is to provide a fluid driven reciprocating pump of the above type but of simpler construction enabling manufacture and maintenance of the pump at lower cost. More particularly, an object of the invention is to provide a pump of the above type but having a simplified control valve arrangement in which the functions of both the main distribution valve and the pilot valve are performed by a single, simplified control valve assembly.